Charcot-Marie-Tooth symptoms usually appear in adolescence or early adulthood, although it is possible for them to occur later. CMT affects motor nerves that send impulses to the muscles and sensory nerves that send impulses to the brain and spinal cord.
Symptoms may include:
- Weakness in the foot and lower leg muscles
- High arches
- Hammer toes
- Foot dropping
- High-stepping gait
- Tripping and falling
- Lower leg taking on an inverted champagne-bottle appearance
- Weakness and a loss of fine motor skills of the arms and hands
Symptoms progress gradually, and pain can be mild to severe. Occasionally, patients experience respiratory muscle weakness. The severity of symptoms varies between patients, even for members of the same family with the condition.
Causes and Risk Factors
Charcot-Marie-Tooth is inherited, and can be passed from one or both parents to a child. More than 70 genes have been linked to the disorder. In some cases, the gene mutation causing CMT has occurred spontaneously in patients’ DNA and is not connected to their parents. These patients may still pass the condition on to their children.
CMT is caused by a mutation in the genes responsible for proteins that affect axons, the nerve fibers sending electrical impulses between the brain and spinal cord to the rest of the body, or the myelin, a coating around the axons that increases the speed at which electrical signals travel.
Without an intact axon and myelin, peripheral nerve cells are unable to signal muscles. This results in muscle weakness and atrophy in the arms, legs, hands or feet. It also can cause problems relaying sensory information from the limbs back to the brain, lessening the ability to feel heat, cold and pain.